Typical transmitter (TX) circuits used for wireline or wireless communications typically comprise digital and analog transmit circuitry. An integral part of most analog transmit circuitry is an analog Power Amplifier (PA). During transmission of data packets, an analog gain of the PA can vary undesirably over a packet time duration, for example, due to physical phenomena, such as temperature variations of circuit components. On a receiving (RX) end, channel estimation can be performed using a packet header of transmitted data packets, wherein the packet header comprises pilot or training symbols. In the 802.11 Wi-Fi standards such training symbols are also referred to as Short Training Field (STF) or Long Training Field (LTF), for example. Any gain variation of the transmitter's PA throughout the packet duration can then cause inaccurate gain estimation and thus limit the performance of a digital radio transmitter or receiver. This performance can be quantified by a measure called Error Vector Magnitude (EVM), for example. This can be critical in products which are required to reach an outstanding EVM (e.g., −35 dB and better), which is already a common requirement for many wireless systems, such as, for example, the 802.11ax Wi-Fi standard supporting up to 1024QAM (Quadrature Amplitude Modulation), which creates the need for receivers to reach an EVM of around −40 dB in Multiple-Input Multiple-Output (MIMO) scenarios.
Thus, there is a need for improving a transmitted signal quality, while at the same time enabling relaxed Radio Frequency (RF) designs.